Image forming apparatus, and developing device and method used in the same

Abstract

Developing device and method in an image forming apparatus are provided which can make it possible maintaining stabilized image by accurately controlling a toner carry amount. A developing roller is supplied with toner from a toner feed roller to form thereon a toner layer by application of a bias voltage to a toner layer forming member which is in pressing contact with the developing roller. When the operation is started (S ), the current flowing from the toner layer forming blade is detected for a predetermined length of time (S ). Based on the detected result, the current toner carry amount is selected, through the operation of CPU and ROM of a controller, from data D which are previously written in ROM (S ). If the selected toner carry amount is determined as an acceptable level that represents a predetermined amount or more (step ), printing operation is started as it is. On the other hand, if the selected toner carry amount is determined as an unacceptable level that is less than the above predetermined amount, the toner carry amount is increased by an amount corresponding to the shortfall by selecting an appropriate feed bias (S , S ).